In this study the leather collectibles of the Inner Mongolia Museum and the Hulunbuir Nationality Museum were analyzed in order to understand the effect of temperature and humidity on the leather. Degradation phenomena of leather collectibles from the Inner Mongolia area were classified and illustrated as described in Silk Collectibles Disease and Illustration (WW/T 00132008). Information was collected on tear force, tensile strength, load elongation and some other physical and chemical properties of the leather samples, before and after their aging by dampheat aging methods. This work provided a preliminary analysis of the influence of temperature and humidity on tanned leather samples and will be helpful to understand causes of the degradation of leather cultural relics. The experiments show that change of humidity is the main cause for degradation of leather cultural relics, which also has an obvious influence on the physical and chemical properties of various tanned leather cultural relics.